Soap-salt complex thickened greases



United States Patent 2,880,174 SOAP-SALT COMPLEX THICKENED GREASFS Arnold J. Morway, Clark, and Herbert K. Wlese, Cranford, NJ., assignors to Esso Research and Engineering Company, a corporation of Delaware No Drawing. Application May 13, 1955 Serlal No. 508,305

13 Claims. (Cl. 252-311) The invention relates to novel organo-metallic complexes or compounds with coordinated valences and to compositions containing the same. More particularly, the present invention pertains to soap-salt complexes comprising metal salt of acetic acid, metal salt of cyclodiene dicarboxylic acids or dienophilic acid derivatives thereof and metal soap of conventional grease-forming high molecular weight carboxylic acids.

In brief compass, the present invention relates to compositions consisting of or containing soap-salt complexes or coordinated compounds consisting of a metal salt of acetic acid, a metal salt of a dicyclopentadiene dicarboxylic acid or a dienophilic carboxylic acid derivative thereof, and metal soap of a high molecular weight fatty acid having from l2 to carbon atoms per molecule. Grease compositions containing the complexes of this invention as thickeners have been found to have excellent load carrying capabilities as well as other desirable grease characteristics. The compositions of the invention also include novel and improved lubricating oils, gear oils, etc.

The use of the so-called soap-salt complexes as grease thickeners is well known in the art. The complex materials used heretofore consisted of combinations of metal soaps of high molecular weight carboxylic acids having from 12 to 30 carbon atoms per molecule and metal salts of low molecular weight carboxylic acids containing from 1 to 6 carbon atoms per molecule. Normally about equimolar proportions of low to high molecular weight carboxylic acids have been employed by the prior art, because of the limited thickening effect of the low molecular weight acid component. It has recently been suggested that highly desirable characteristics such as load carrying ability can be imparted to compositions of that sort by increasing the low molecular weight acid content,

so that they contain at least 7 moles and up to moles or more of the low molecular weight acid per mol of the high molecular weight acid.

It has now been found that novel soap-salt complexes can be prepared by employing a metal salt of acetic acid, at least one metal soap of a high molecular weight carboxylic acid and a metal salt of a cyclodiene dicarboxylic acid, e.g. dicyclopentadiene dicarboxylic acid, or polycarboxylic acid derivatives thereof obtained by reacting dicyclopentadiene dicarboxylic acid or the like with maleic anhydride or other similar dienophilic carboxylic compounds. It has also been found that when the combination of acids described above is employed a mol ratio of acetic acid to the other acids about 4:1 to 40:1, preferably about 7:1 to 12:1, and a mol ratio of the cyclodiene dicarboxylic acids or polycarboxylic acid derivatives to the high molecular weight carboxylic acids about 0.5 l to 5:1, preferably about 0.5 :1 to 2:1, can be efiectively utilized to prepare the novel soap-salt complexes of the invention.

Dicyclodiene dicarboxylic acids suitable for the pur' poses of this invention have been previously described in 2,880,174 Patented Mar. 31, 1959 ice a copending application of Cohen et 111., Serial No. 268,- 122, filed January 24, 1952, patented August 30, 1955, as US. Patent No. 2,716,662, and since designated Re. 24,123, reissued February 28, 1956. These acids are actually dimers of the corresponding monocyclodiene monocarboxylic acids. By cross-polymerizing the dimer acids with dienophilic acid compounds such as maleic anhydride, a valuable tricarboxylic acid or anhydride thereof will be obtained which can'be used in the preparation of the novel soap-salt complexes of the invention. The cross-polymerization reaction may be illustrated by the following steps:

The reaction product is a derivative of bicycloheptene and can be termed a carboxy substituted bicyclo (2,2,1)- 5-heptene-2,3-dicarboxylic anhydride. It can also be designated as a monocarboxy substituted 3,6-methylene-4- cycloheXeneLZ-dicarboxylic acid anhydride. This anhydride is capable of existing in either the endo or exo isomeric form; the ratio of endo and exo being a function of the reaction temperature. The higher the temperature, the greater the amount of endo isomer produced.

Though dicyclopentadiene dicarboxylic acid is shown above, other dicarboxylated dicyclodiene compounds that can be employed include dimethyl dicyclopentadiene dicarboxylic acid, i.e. the dicarboxylated dimer of methyl cyclopentadiene, and methyl dicyclopentadiene dicarboxylic acid, i.e. the mixed dimer of cyclopentadiene carboxylic acid and methyl cyclopentadiene carboxylic acid. The corresponding alkyl esters such as the dimethyl ester of dicyclopentadiene acid can also be utilized.

Maleic anhydride is the preferred dienophilic unsaturated carboxylic compound. Itaconic acid or itaconic anhydride can be also used, however, to yield another species of dicycloheptene tricarboxylic acid or the corresponding tricarboxylic acid anhydride. Condensation of cyclopentadiene carboxylic acids with aconitic acid will result in a tetracarboxylic acid. The structure of the tetracarboxylic acid product is represented by the follow ing formula:

-COOH It can be designated as a tetra-carboxy substituted 3,6- methylene-4-cyclohexene l carboxymethylene 1,2 di carboxylic acid.

Thus the polycarboxylated bicycloheptenes capable of being utilized in the preparation of the mesh complex thickeners of the invention can correspond to the general formula COOH wherein R can be either a hydrogen or a methyl group and R either a hydrogen or a carboxymethylene group.

In general, it is desirable to use the condensation reactants in stoichiometric proportions, i.e. about one mol of unsaturated dienophilic acid or anhydride per half mol of the dimeric cyclodiene carboxylic acid, though an excess of either reactant may be present.

Temperatures within the range of about 75 to 250 C., preferably between about 135' and 190 C., are employed. Below about 100' C. the reaction tends to become slow due to the low rate of depolymerization of the dimer and the resulting low availability of the monomeric acid reactant. n the other hand, temperatures above 190 C. tend to decarboxylate the cyclodiene carboxylic acid and cause resinification. The pressure depends on the dienophilic acid employed and the temperature at which the reaction is carried out. Accordingly, the reaction may be conveniently conducted at pressures ranging from atmospheric or slightly subatmospheric to moderately elevated pressure such as 10 to 50 p.s.i.g. The reaction is normally completed in about to 60 minutes, and it can be carried out either batchwise or in a continuous manner.

The reaction temperature is suitably controlled by refluxing a solvent medium such as xylenes, mineral spirits, nonane, decalin, tetralin, propionic acid, acetic acid, or similar liquids, particularly hydrocarbons or saturated aliphatic acids, which are substantially inert in the reaction mixture and boil in the desired reaction temperature range under suitable pressure. By employing other temperature control means, the reaction can be carried out without a solvent medium.

The high molecular weight monocarboxylic acids use ful for preparing the soap-salt complexes of the invention contain from about 12 to 30, preferably from 18 to 22, carbon atoms per molecule. These acids may be derived from saturated or unsaturated naturally occurring or synthetic fatty material. The fatty acids normally used in the manufacture of conventional greases, and particularly the more saturated acids are preferred. Examples of such acids include lauric, myristic, palmitic, stearic, monoand poly-hydroxy stearic and arachidic acids and the hydrogenated fish oil and tallow acids, which contain chiefly stearic acid. However, unsaturated acids such as oleic, ricinoleic, and the like may also be used. The average saponification value of a suitable mixture of the high molecular weight carboxylic acid should not be more than about 300, and preferably not more tha about 220.

The acetic acid employed in the present invention can either be glacial acetic acid or an aqueous solution of acetic acid. If an aqueous solution is employed, the concentration of acid in the solution may vary from about 60 to 99.9 wt. percent, and is preferably about 80 wt. percent. Glacial acetic acid is, however, preferred. The presence of a salt of acetic acid in the complex is an essential part of the present invention, but the use of a substituted acetic acid having two carbon atoms per molecule is not excluded, where such modification may be desirable. For example, chloro-acetic acid, glycolic acid, thioglycolic acid, glysine or oxalic acid may be used to modify the structure of a grease made in accordance with the invention.

The metallic constituent of the soap-salt complexes is employed in a form which can combine chemically with carboxylic acids to form salts or soaps. Ordinarily, the

metal hydroxide is used. The alkaline earth metal hydroxides or carbonates such as those of calcium, barium and strontium are particularly useful for the purposes of this invention. Calcium hydroxide is especially preferred. In general, divalent metals such as alkaline earth metals are superior in this respect to the alkali metals, i.e. sodium, potassium and lithium. Other suitable divalent metals include magnesium and zinc.

The soap-salt complex thickener may be utilized in combination with a wide variety of mineral as well as synthetic lubricating oils. Mineral base lubricating oils ranging in viscosity from about 50 to 2000 SUS at F. are preferably employed as the liquid phase of the grease composition within the range of about 50 to 95 wt. percent, based on the total weight of the final grease composition. These naturally occurring mineral lubricating oils may be derived from any petroleum crude source, whether paraffinic or naphthenic in type, and may be refined by any of the well known refining techniques.

Suitable synthetic lubricating oils are the hydrocarbon, hydrocarbon polymer, ester, complex ester, formal, mercaptal, polyalkylene oxide, silicone or similar types. More particularly, synthetic oils such as di-2-ethylhexyl sebacate, di-C; Oxo azelate, and other branched chain simple esters of dicarboxylic acids as well as complex esters prepared from glycols, dicarboxylic acids and alcohols or monocarboxylic acids.

The metal soap-salt complexes of the invention may be prepared by coneutralization of a mixture of the carboxylic acids with suitable bases, hydroxides or carbonates of the desired metals. The coneutralization step may be carried out in situ in the liquid menstruum to which the complex is to be applied in actual use. Thus, for example, the mixture of acids may be coneutralized in a portion or all of a lubricating oil which then forms the dispersant of the complex and is thereby gelled to a grease. In a similar manner the coneutralization may be carried out in other dispersants or solvent fluids, the characteristics of which are to be modified by the complex. The coneutralized material is heated to a temperature above about 400 F., preferably 435' to 550 F., in order to dehydrate it and form the complex. When this heating step is carried out in a liquid dispersant, the latter should have a boiling point above 400' F. or the heating should be carried out under pressure.

The high metal content soap-salt complex can also be prepared by separately preforming at least a portion of the acetic acid salt, the salt of cyclodiene dicarboxylic acid or dienophilic adducts thereof and the high molecular weight carboxylic acid soap. The preformed materials are then intimately mixed and heated under complex forming conditions.

The complex compounds of the invention when pre pared in a liquid dispersant or solvent may be isolated from their dispersions or solutions by solvent extraction of the dispersing medium in a solvent in which the complex is insoluble. Suitable solvents include most of the hydrocarbon solvents, acetone, etc.; the proper choice depending on the solubility characteristics of the liquid menstruum used to disperse the complex.

In general, the lubricating grease compositions thickened with the complexes of the invention are prepared by mixing together the desired amount of mineral and/ or synthetic lubricating oil, the high molecular weight carboxylic acid, the cyclodiene dicarboxylic acid or dienophilic carboxylic acid derivative thereof and the base. The mixture is warmed while mixing to a temperature of about 90 to F., but preferably just suflicient to melt the high molecular weight acid. The acetic acid is then added to the mixture and allowed to react without further external heating. When the temperature of reaction starts to subside, external heating is then applied and is continued until the temperature is about 400 to 550' F., preferably about 435 to 550 F. At this point, heating is discontinued, and the grease batch is cooled to a tem perature of about 250' to 290' F. Any of the conventional anti-oxidant additives, such as phenyl alpha-naphthylamine can then be added, and the grease is further cooled to below about 200' F., preferably about 180' F. The resulting grease composition may be homogenized by passing it through a Morehouse mill or Gaulin type homogenizer.

In one particular embodiment, these high metal content soap-salt complexes are incorporated in mineral or syntheic lubricating oils in grease-making proportions of about 5 to 40 wt. percent, preferably 10 to 30 wt. percent, to produce greases of excellent extreme pressure and structural stability characteristics.

The invention will be more fully understood by reference to the following specific examples illustrating various modifications of the invention.

EXAMPLE 1 A number of mineral oil base lubricating grease compositions having the formulations and properties given in Table I below were prepared as follows:

Grease A.--All of the mineral lubricating oil, the dicyclopentadiene dicarboxylic acid, the stearic acid and the hydrated lime were charged to a fire heated kettle and thoroughly mixed while heating to 135' F. The acetic acid was then added to the mixture and heating was continued to 500 F. The resulting grease composition was then cooled to 275 F., and the phenyl alpha naphthylamine added. The grease was further cooled to 180' F. and then Gaulin homogenized at 6000 p.s.i.

Grease B.The grease was prepared substantially as described in the preparation of grease A.

Table l Grease No A B Formulations (Percent Wt.):

Glacial acetic acid 12.0 12.0. Dlcyclopcntadiene dicarboxylic aci 4 8.0 Stearic acid- 2 3.0. Hydrated lim 9 0.7. Phenyl alpila-uaphthylamine- 0.5. Mineral lubricating oil (55 BUS/210 R).-. 71.0 71.8 Moi ratio of acetic to higher acids 8 8.8. Moi ratio of DCPDA I to stearic acid... 2.0 1.8. Sap. No. (Ex acetic) 400 858. Propcrtics:

Appearance Uniform, Uniform,

' remtsol fluid. Dropping Point, F 500+. Penetrations (77 F., mm./10):

Unworked. 302. Worked 60 str 820. Worked l0.000 strokes 845. Phase changes up to 400 F-..- Ltgg lcatiun Life, hrs.: 10,000- r.p.m.- 1,900+. Norma-Hoffman Oxidation Test (hrs. to 400+ 400+.

p.s.i. drop). E. P. Properties:

Timken Test (40 lbs. load) Pass Pass. BAE Scale Rdg. (1.000 r.p.m.)......... 340

1 Dicyclopentadiene dicarboxylic acid. 1 Not a failure (test discontinued). Contains an additional 0.5% phenyl alpha-naphthylamine.

It will be noted that both grease A and 13 had excellent extreme pressure properties as well as other desirable grease characteristics such as high dropping points, oxidation resistance, etc. onstrate that by controlling the respective amounts of the cyclodiene dicarboxyiic and high molecular weight carboxylic acids employed the consistency of the final grease composition can be varied. In grease B, for example, a uniform solid grease composition was obtained with a moi ratio of dicyclopentadiene dicarboxylic acid to stearic acid of about 1.3, whereas with a higher ratio of about 2.6, grease A had a semi-fluid consistency. In general, moi ratios of about 0.5 to 2 should be employed in order to obtain solid firm grease structures in accordance with the invention.

Moreover, the above data dem- EXAMPLE II Grease C was prepared from the following ingredients:

In lients Percent m Weight Glacial acetic acid. 12. 0 Btaario acid 4. 0 Mailei anhydridedicyciopcntadlcne dicarboxyiic acid ad 2 0 nc Hydrated lim 0. 8 Phenyl alpha-naphthylamine 1. 0 Mineral lubricating oil S08 210 F.) 71. 2 Equivalent saponiilcation num r of acids (Ex. aoettc).. 397 Moi ratio of acetic to hi her acids 8. 5 -Mol ratio of MA-DCP A adduct to stearle acid 0. 67

l A carboxy substituted methylene 4-cyclohexcne-L2 dicarhoxylic acid anhydride. Prepared by reacting dicyclopontadiena dlcarboxylic acid :tith lrnalcic anhydride in equlmoiar proportions at. 135 F. in the presence xy ene.

PREPARATION All of the mineral lubricating oil, the stearic acid, the

carboxy substituted 3,6-methylene-4-cyclohexene-1,2-dicarboxylic acid anhydride, and the hydrated lime were charged to a fire heated kettle and warmed while mixing to 135 F. The acetic acid was then added and heating was continued to 510'F. The grease batch was then cooled to 250 F. and the phenyl alpha-naphthyiamine added. The grease batch was further cooled to 180 F. and then homogenized in a Gaulin homogenizer at 6500 p.s.i.

Wheel hearing test (6 hrs. Pass.

-200 F. Norma-Hoffman oxidation test (hrs.

to 5 p.s.i. drop) 400+.

It will be noted grease C passed both a 40 lb. load on the Timken E.P. testing machines and a shock load of 15 weights in the Almen test, and thus this grease is capable of withstanding high unit bearing loads. In addition, the grease is relatively easy to manufacture, shows no dropping point, and is insoluble in boiling water. Though the grease had an unworked penetration of 265 mm./ l0, it softened to 350 mm./i0 after being worked for strokes in an ASTM worker. After 100,000 strokes, the grease had a temperature of 118' F. and a penetration of 274 mm./10. When the grease was cooled to 77 F. again and reworked 60 strokes it had a penetration of 345 mm./ 10. By heating the grease, while working, to temperatures of 200 and 300' F., penetrations of 270, 250 and 245 mm./l0, respectively, were obtained. It is shown, therefore, that grease can be easily pumped or dispensed at ambient temperatures,

a while at operating bearing temperatures the grease would The invention is not necessarily limited to the specific conditions and materials of the foregoing examples. These conditions and materials may be varied within the limits indicated in the general portions of the specification. Moreover, the conventional grease additives such as oxidation inhibitors, pour point depressors, corrosion inhibitors and the like, may be used in usual proportions, as will be understood by those skilled in the art.

What is claimed is:

1. A dehydrated soap-salt complex comprising at least one metal soap of a high molecular weight aliphatic carboxylic acid having from about 18 to 22 carbon atoms per molecule; a metal salt of a polycarboxylic acid material selected from the group consisting of dicyclodiene dicarboxylic acid, polycarboxylated bicyclohcptene having the formula wherein R is selected from the group consisting of hydrogen and a methyl radical and R is selected from the group of hydrogen and a carboxymethylene radical, and tricarboxylated bicycloheptene acid anbydride; and a metal salt of acetic acid, in which the mo] ratio of acetic acid to the other carboxylic acids is about 4:1 to 40:1 and the mol ratio of the polycarboxylic acid material to the high molecular weight carboxylic acid is about 0.5 :1 to :1, said metal constituents being selected from the group consisting of alkaline earth metals and zinc.

2. A dehydrated soap-salt complex comprising at least one alkaline earth metal soap of a high molecular weight carboxylic acid having from 12 to 30 carbon atoms per molecule, an alkaline earth metal salt of dicyclopentadiene dicarboxylic acid and an alkaline earth metal salt of acetic acid, in which the mol ratio of acetic acid to the other carboxylic acids is about 7:1 to 12:1 and the mol ratio of the dicyclopentadiene dicarboxylic acid to the high molecular weight carboxylic acid is about 0.5:1 to 5:1.

3. The soap-salt complex of claim 2 wherein said alkaline earth metal is calcium.

4. The soap-salt complex of claim 2 wherein the mol ratio of dicyclopentadiene dicarboxylic acid to high molecular weight acid is about 0.5:1 to 2:1.

5. A dehydrated soap-salt complex comprising at least one alkaline earth metal soap of a high molecular weight carboxylic acid having from 12 to 30 carbon atoms per molecule, an alkaline earth metal salt of a polycarboxylated bicyclo (2,2,1)-heptene and an alkaline earth metal salt of acetic acid, in which the mol ratio of acetic acid to the other carboxylic acids is about 7:1 to 12:1 and the mol ratio of polycarboxylated bicyclo (2,2,l)-heptene to the high molecular weight carboxylic acid is about 0.5 :1 to 2:1.

6. The soap-salt complex of claim 5 wherein said polycarboxylated bicyclo (2,2,1)-heptene is a tri-carboxy substituted 3,6-methylene-4-cyclohexene-1,2-dicarboxylic acid.

7. The soap-salt complex of claim 5 wherein said polycarboxylated bicyclo (2,2,l)-heptene is a tetra-carboxy substituted 3,6-methylene-4-cyclohexene-1-carboxymethylene-LZ-dicarboxylic acid.

8. The soap-salt complex of claim 5 wherein said polycarboxylated bicyclo (2,2,1)-heptene is a carboxy substituted 3,6-methylene-4-cyclohexene-1,2-dicarboxylic acid anhydride.

9. The method of preparing a dehydrated soap-salt complex which comprises mixing together acetic acid, at least one high molecular weight carboxylic acid having from 12 to 30 carbon atoms per molecule and a polycarboxylic acid material selected from the group consisting of dicyclodiene dicarboxylic acid and polycarboxylated bicyclo (2,2,1)-heptene, in a mol ratio of acetic acid to other carboxylic acids of about 4:1 to 40:1 and a mol ratio of polycarboxylic acid material to high molecular weight carboxylic acid of about 0.5 :l to 5: 1, reacting the mixed acids with an alkaline earth metal base sufiicient in amount and under conditions to form a mixture of metal soap and salts of said acids, dehydrating said mixture and heating said dehydrated mixture to complexforming temperatures in the range of 400 to 550 F.

10. The method of claim 9 in which said soap-salt complexes are prepared in a mineral lubricating oil dispersant.

11. A lubricating grease composition comprising a major proportion of a lubricating oil and a minor greasemaking proportion of a soap-salt complex consisting of at least one alkaline earth metal soap of a high molecular weight fatty acid having from about 18 to 22 carbon atoms per molecule, an alkaline earth metal salt of a polycarboxylic acid material selected from the group consisting of dicyclodiene dicarboxylic acid and tricarboxylated bicyclo (2,2,l)-heptene, and an alkaline earth metal salt of acetic acid, in which the mol ratio of acetic acid to the other carboxylic acids is about 4:1 to 40:1 and a mol ratio of polycarboxylic acid material to high molecular weight fatty acid is about 0.5:1 to 5:1.

12. The grease composition of claim 11 in which the lubricating oil is a mineral lubricating oil.

13. The method of preparing a lubricating grease composition which comprises dispersing an alkaline earth metal base, at least one high molecular weight carboxylic acid having from 12 to 30 carbon atoms per molecule, and a polycarboxylic acid material selected from the group consisting of dicyclodiene dicarboxylic acid and polycarboxylated bicyclo (2,2,l)-heptene in a dispersing proportion of a mineral lubricating oil, heating the dispersion to a temperature of about to F., adding acetic acid to the dispersion, and heating the resulting mixture to a complex-forming temperature in the range of 400' to 550 F. and then cooling to obtain said lubricating grease composition, the mol ratio of acetic acid to the other carboxylic acids being about 4:1 to 40:1 and the mol ratio of polycarboxylic acid material to high molecular weight carboxylic acid being about 0.5:1 to 5:1.

References Cited in the tile of this patent UNITED STATES PATENTS 2,197,263 Carmichael et al. Apr. 16, 1940 2,417,428 McLennan Mar. 18, 1947 2,564,561 Carmichael et al. Aug. 14, 1951 2,628,195 Allison et al. Feb. 10, 1953 2,699,428 Lux et al. Jan. 11, 1955 2,716,662 Cohen et al. Aug. 30, 1955 2,758,973 Morway et al Aug. 14, 1956 OTHER REFERENCES Boner: Lubricating Greases," chapter 16, pages 615- 675, Reinhold Pub. Corp., New York, N.Y., 1954. 

11. A LUBRICATING GREASE COMPOSITION COMPRISING A MAJOR PORTION OF A LUBRICATING OIL AND A MINOR GREASEMAKING PROPORTION OF A SOAP-SALT COMPLEX CONSISTING OF AT LEAST ONE ALKALINE EARTH METAL SAOP OF A HIGH MOLECULAR WEIGHT FATTY ACID HAVING FROM ABOUT 18 TO 22 CARBON ATOMS PER MOLECULE, AN ALKALINE EARTH METAL SALT OF A POLYCARBOXYLIC ACID MATERIAL SELECTED FROM THE GROUP CONSISTING OF DICYCLODIENE DICARBOXYLIC ACID AND TRICARBOXYLATED BICYCLO (I,2.1)-HEPTENE, AND AN ALKALINE EARTH METAL SALT OF ACETIC ACID, IN WHICH THE MOL RATIO OF ACETIC ACID TO THE OTHER CARBOXYLIC ACIDS IS ABOUT 4:1 TO 40:1 AND A MOL RATIO OF POLYCARBOXYLIC ACID MATERIAL TO HIGH MOLECULAR WEIGHT FATTY ACID IS ABOUT 0.5:1 TO 5:1. 